/*
    GNU GENERAL LICENSE
    Copyright (C) 2006 The Lobo Project. Copyright (C) 2014 - 2016 Lobo Evolution

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public
    License as published by the Free Software Foundation; either
    verion 3 of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    General License for more details.

    You should have received a copy of the GNU General Public
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
    

    Contact info: lobochief@users.sourceforge.net; ivan.difrancesco@yahoo.it
 */
/*
 * $Id: XPathExpressionImpl.java 1225426 2011-12-29 04:13:08Z mrglavas $
 */

package org.lobobrowser.html.xpath;

import javax.xml.transform.TransformerException;

import org.apache.xpath.XPath;
import org.apache.xpath.XPathContext;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.res.XPATHErrorResources;
import org.apache.xpath.res.XPATHMessages;
import org.lobobrowser.w3c.xpath.XPathException;
import org.lobobrowser.w3c.xpath.XPathExpression;
import org.lobobrowser.w3c.xpath.XPathNamespace;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;

/**
 *
 * The class provides an implementation of XPathExpression according to the DOM
 * L3 XPath Specification, Working Group Note 26 February 2004.
 *
 * <p>
 * See also the
 * <a href='http://www.w3.org/TR/2004/NOTE-DOM-Level-3-XPath-20040226'>Document
 * Object Model (DOM) Level 3 XPath Specification</a>. </p>
 *
 * <p> The <code>XPathExpression</code> interface represents a parsed and
 * resolved XPath expression. </p>
 *
 * @see org.w3c.dom.xpath.XPathExpression
 *
 * @xsl.usage internal
 */
public class XPathExpressionImpl implements XPathExpression {

	/** The xpath object that this expression wraps. */
	final private XPath m_xpath;

	/**
	 * The document to be searched to parallel the case where the XPathEvaluator
	 * is obtained by casting a Document.
	 */
	final private Document m_doc;

	/**
	 * Constructor for XPathExpressionImpl.
	 *
	 * @param xpath
	 *            The wrapped XPath object.
	 * @param doc
	 *            The document to be searched, to parallel the case where'' the
	 *            XPathEvaluator is obtained by casting the document.
	 */
	XPathExpressionImpl(XPath xpath, Document doc) {
		m_xpath = xpath;
		m_doc = doc;
	}

	/**
	 *
	 * This method provides an implementation XPathResult.evaluate according to
	 * the DOM L3 XPath Specification, Working Group Note 26 February 2004.
	 *
	 * <p>
	 * See also the <a href=
	 * 'http://www.w3.org/TR/2004/NOTE-DOM-Level-3-XPath-20040226'>Document
	 * Object Model (DOM) Level 3 XPath Specification</a>. </p>
	 *
	 * <p> Evaluates this XPath expression and returns a result. </p>
	 *
	 * @param contextNode
	 *            The <code>context</code> is context node for the evaluation of
	 *            this XPath expression.If the XPathEvaluator was obtained by
	 *            casting the <code>Document</code> then this must be owned by
	 *            the same document and must be a <code>Document</code>,
	 *            <code>Element</code>, <code>Attribute</code>,
	 *            <code>Text</code>, <code>CDATASection</code>,
	 *            <code>Comment</code>, <code>ProcessingInstruction</code>, or
	 *            <code>XPathNamespace</code> node.If the context node is a
	 *            <code>Text</code> or a <code>CDATASection</code>, then the
	 *            context is interpreted as the whole logical text node as seen
	 *            by XPath, unless the node is empty in which case it may not
	 *            serve as the XPath context.
	 * @param type
	 *            If a specific <code>type</code> is specified, then the result
	 *            will be coerced to return the specified type relying on XPath
	 *            conversions and fail if the desired coercion is not possible.
	 *            This must be one of the type codes of <code>XPathResult</code>
	 *            .
	 * @param result
	 *            The <code>result</code> specifies a specific result object
	 *            which may be reused and returned by this method. If this is
	 *            specified as <code>null</code>or the implementation does not
	 *            reuse the specified result, a new result object will be
	 *            constructed and returned.For XPath 1.0 results, this object
	 *            will be of type <code>XPathResult</code>.
	 * @return The result of the evaluation of the XPath expression.For XPath
	 *         1.0 results, this object will be of type <code>XPathResult</code>
	 *         .
	 * @exception XPathException
	 *                TYPE_ERR: Raised if the result cannot be converted to
	 *                return the specified type.
	 * @exception DOMException
	 *                WRONG_DOCUMENT_ERR: The Node is from a document that is
	 *                not supported by the XPathEvaluator that created this
	 *                <code>XPathExpression</code>. <br>
	 *                NOT_SUPPORTED_ERR: The Node is not a type permitted as an
	 *                XPath context node.
	 *
	 * @see org.w3c.dom.xpath.XPathExpression#evaluate(Node, short, XPathResult)
	 * @xsl.usage internal
	 */
	@Override
	public Object evaluate(Node contextNode, short type, Object result) throws XPathException, DOMException {

		// If the XPathEvaluator was determined by "casting" the document
		if (m_doc != null) {

			// Check that the context node is owned by the same document
			if ((contextNode != m_doc) && (!contextNode.getOwnerDocument().equals(m_doc))) {
				String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_DOCUMENT, null);
				throw new DOMException(DOMException.WRONG_DOCUMENT_ERR, fmsg);
			}

			// Check that the context node is an acceptable node type
			short nodeType = contextNode.getNodeType();
			if ((nodeType != Node.DOCUMENT_NODE) && (nodeType != Node.ELEMENT_NODE) && (nodeType != Node.ATTRIBUTE_NODE)
					&& (nodeType != Node.TEXT_NODE) && (nodeType != Node.CDATA_SECTION_NODE)
					&& (nodeType != Node.COMMENT_NODE) && (nodeType != Node.PROCESSING_INSTRUCTION_NODE)
					&& (nodeType != XPathNamespace.XPATH_NAMESPACE_NODE)) {
				String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_NODETYPE, null);
				throw new DOMException(DOMException.NOT_SUPPORTED_ERR, fmsg);
			}
		}

		//
		// If the type is not a supported type, throw an exception and be
		// done with it!
		if (!XPathResultImpl.isValidType(type)) {
			String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_INVALID_XPATH_TYPE,
					new Object[] { new Integer(type) });
			throw new XPathException(XPathException.TYPE_ERR, fmsg);
		}

		// Create an XPathContext that doesn't support pushing and popping of
		// variable resolution scopes. Sufficient for simple XPath 1.0
		// expressions.
		// Cache xpath context?
		XPathContext xpathSupport = new XPathContext(false);

		// if m_document is not null, build the DTM from the document
		if (null != m_doc) {
			xpathSupport.getDTMHandleFromNode(m_doc);
		}

		XObject xobj = null;
		try {
			xobj = m_xpath.execute(xpathSupport, contextNode, null);
		} catch (TransformerException te) {
			// What should we do here?
			throw new XPathException(XPathException.INVALID_EXPRESSION_ERR, te.getMessageAndLocation());
		}

		// Create a new XPathResult object
		// Reuse result object passed in?
		// The constructor will check the compatibility of type and xobj and
		// throw an exception if they are not compatible.
		return new XPathResultImpl(type, xobj, contextNode, m_xpath);
	}

}
